Data Acquisition

Some of its features include:• True bus master capabilities.• Additional DMA transfer modes, such as block demand or block burst mode.• Ability to share interrupt lines between devices.• Automatic expansion board configuration so as to achieve a conflict free system.While the speed of the EISA slot is still limited to 8 MHz because of the ISA compatibilityrestriction, the increased bus-width allows a much higher data transfer rate (33 MHz). Inburst mode, speeds up to 40 MHz can be achieved. Unfortunately, benchmarks show thatEISA expansion cards are no faster than their ISA equivalents, largely due to the fact that fewEISA peripherals make use of the extra speed features such as bus mastering.4.8.4 The PCI, compactPCI, and PXI busIn the spring of 1991 Intel Corporation began working on the PCI bus as an internal project.Intel engineers were concerned that the existing input / output (I/O) bus bandwidths were notkeeping up with current CPU speeds and were falling even farther behind as the newgenerations of CPU’s (486 / Pentiums) were becoming available.The ISA bus was introduced by IBM in 1981 and was upgraded to 16 bit with theintroduction of the AT in 1984. The ISA originally ran at 4.77 MHz. The top speed was8 MHz. In 1987, the MCA (micro channel for the PS/2) was introduced. This bus didn't lastlong (neither did the PS/2). The MCA was a 16- or 32-bit bus that ran at 10 MHz. The EISAbus was presented in 1989. It was a 32-bit, 8MHz bus with the big advantage of more pinouts for larger cards. In 1992 the CPU VL bus was developed. It was a 32-bit bus running at33 MHz. In 1993 the PCI was introduced. At first, it ran at the same 33 MHz, but soon thespeeds increased to 100 MHz on 3.3 volt CPUs. The PCI bus can use either 32- or 64-bit buslines.Year Bus Bits Frequency1981 IBM PC ISA 8 4.771984 IBM AT ISA 16 6/81987 MCA (PS/2) 16/32 101989 EISA 32 81992 VL 32 331993 PCI 32 331995 PCI 32/64 33/661996 PCI 32/64 1001998 PXI same as PCITable 4.5Growth table of the PC bus systemThe PCI or (Personal Computer Interface bus) is a relatively new addition to the PCmotherboard. As time goes on it seems that personal computers have more and more PCIslots and less and less ISA or EISA SLOTS. Very soon all computers will have PCI slots butno ISA or EISA slots. Is this one of those transitional things that we have to put up with in anever-changing industry, or is the PCI that much better? The answer to that question is that thePCI bus is that much better. Legacy bus systems such as the ISA and EISA were good in thedays when only one application was running at a time. Now that the PC can run more than